Continuous blow ring for filters



July 19, 1949. F. w. ARNOLD 2,476,942

CONTINUOU S BLOW RING FOR. FILTERS 2 Sheets-Sheet 1 Filed A ril 28, 1948 INVENTOR.

July 19," 1949. F. w. ARNOLD CONTINUOUS BLOW RING FOR FILTERS 2 Sheets-Sheet 2 Filed April 28, 1948 Patented July 19, 1949 U N! TED S T O'FFI CE CGNTENUOUS BLOW RING FQR Frederick l ltpArnoli-iChatham,:Nu 1.,5assignor: to -;Pulverizing 'iMachinery (30., Summit, :N. :J.., a corporation .of New Jersey Application April '28, 1948,1 Serial'Nh. 233792 3 Claims.

This invention relates to self-cleaning dust filters of the type in which the filter itself is'a vertical tube or cylindrical bag of closely woven fabric, such as felt. The dust-laden gas, usually air, is

introduced into the interior of the filter tubeadiacent its upper end and the dust-free air escapes outwardly through the interstices of the felt, leaving a layer of dust on the inner surface of the tube. This layer, together with any dust which is caught in the interstices of the felt, is removed by blowing relatively high pressure air from a ring surrounding the tube through the felt from the outside. This ring has a slot around its innerpe riphery for the discharge of such highpressure air. To insure that the air issuing from the slot passes through the felt, the inner diameter of the cleaning airor blowring ismade less .than the outer diameter of the tube when distended. The

ring is reciprocated slowly up and down the'fiiter bag so as to clean successively the whole bag. The

air passing from the blow ring through' the felt into the interior of the filter tube eventually escapes outwardly through the portionsof the felt not in contact with the ring.

It has been found that it'is highlyimportan't to get the right proportion between the diameter of the tube andthat ofthe ring. If the diameters are too nearly the same, there is leakage of air between the outside of the filter tube and the'ring.

If the diameter of the tube is too large with respect to that of the. ring, the tube is wrinkled and sired diameter. Then again, the felt bag stretches or contracts with variations in humidity. Wear also changes-the dimensions'of the bag. iE-orthese reasons the ring has been made discontinuous with its ends separated so that, by increasing or decreasing such separation, the inner :diameter of the ring could be increased or decreased aproportinately.

The separation of the ends of the blow :ring leavesa gap permitting a convex verticalfluteto form in the felt as the latter is pushedoutwardly by the internal air pressure into such gap. This isapt to produce excessive wear along the-verticalsection of thefilter bag registering with.- such gap. This is particularlythe case when the .filter is assembled'so that its longitudinal seam registers with the gap.

The object of the present invention is to provide a blow ring whose internal diameter can be varied without presentinga gap into which-theflfiltertu'be can be pushed outwardly.

According :"to the present invention, therefore, the :ring is discontinuous with one end in sliding telescopic engagement-with the other. Thissliding telescopic engagement is conveniently' br'ought about by integrally securing to'one end of the blow ring an extension 'ofcylindrical form havi ng ani'inner transverse radius of curvature equal 'to the outer transverse radius of curvature of the tubeforming theblow ring, or vice versa.

It is diificult to-provideanair-tight telescopic connection when the two parts are curved longitudinally, especially when, 'as .in this case, externally arranged packing glands are impracticable as external projections of any kind must be: avoided. For this and/other reasona'it is de- 'sirable 'to I place closures i transversely across "the bore of 'the ring neareaeh end thereo'fgso that a closed chamber is-produced extending nearly but notquite completely around the fe'lt tube.

Itwnr be "evident that where such *clos uses are used, it is not essential that either one or' b'o'th'of the overlapping end portion-or portions extend all around the-ring "ina transverse plane. To prevent a gap be'tween -theendsof the blow r'ing into "which the -filter-tube canbe' pushed outwardly, it issufiicient if such'overlappingportion orpor'tions bridge the gap "only -on'that side df-theblow ring next the felt. Hence. where i the 't'e'rm telescopic engagement or *connection'is used "to define the scope of "this invention, -it should be understood that it is tdbeinterpreted br'oadly'enough to include a construction in which the overlapping slidingportions br'idge'the gap between-the ends 'of-the blow ring-only on that side of-theblow'ring next the felt.

Two suitable forms of construction are shown. by way of example, in the "accompanying "dravh ings, wherein:

-Fi'g. lis -aside elevation of "a filter embodying the present invention;

Fig. is a-plan viewofthe blow ring;

Fig."3"is 'a front elevation of the blow; ring;

Fig.4 is asectionon the line 44"of Fig.1;

Fig.- 5'isawection the line 55 of Fig. "6,;

Figfiliistaifront'view of'the'bl'owringadjusting mechanisms .Fig. '7 "is fa section 'on the Jline "l-1 of Fig. 6; and

Fig. *8is "a sectional view 's'imilartdFig. 5 of a modifiediormof construction. a

The Ifilter comprisesia tube Illxof suitable filtering material, .preferab ly felt,'attach'ed at its .upper and to a 'do'wnwar'cllyexten'din flange 'on a circular -closure ll. This .closure .isihunjg from a platform 12 ,byfbolts I13. .Thisplatform, .in turn, is suspendedifromthe floor above bybolts I' l.

fihelowerend o'f'the tube'l'll isfsecured'to the top .of .a..hopper I'L'terniinating in a discharge spout. i8. iIhebag'is held taut. in a=vertical direcdust concentration is not mixed with the air in the lower part of the tube having 'a very high dust concentration. The air so introduced escapes outwardly through the pores of the filter leaving the dust behind on the inner surface of the filter and to some extent in the interstices in the superficial portions of the filter material. Unless such dust was periodically removed, the fiow of air would get less and less and the pressure required to force it through the filter would progressively increase. 7

Removal of dust is accomplished by reversal of air flow. For this purpose a cleaning air or blow ring is provided'having an internal diameter slightly less than the external diameter of the filter tube when distended by the pressure of the dust-laden air. Along its inner periphery, this ring has a series'of slots 25-for the discharge of the relatively high pressure cleaning air. This air is supplied through a flexible hose 2'! from an air-pump 28 drivenby motor 29.

The blow ring isreciprocated up and down the filter tube by means of two chains 32 arrangedon diametrically opposite sides of the filter tube. These chains pass over pairs of sprocket wheels 33 and 34. The sprockets 33 are driven continuously in unison through a worm reduction gear by motor 29. V i

The blow tube is connected to each chain 32 by two chain lengths 35 and 31, each connected at one end to a pin 38 on the blow ring and at their other ends to'pins 39 and 40 projecting laterally from the sprocket chain. These chain lengths 3t and 31 are longer than the diameter of the sprocket wheels 33 so that, at the end of the upward movement of the blow ring, when the pins 39 and 4!! pass over the tops of the sprocket wheels 7 33, the pins 38 are sprockets.

below the bottoms of such At the end of its downward movement, the blow ring rests on the top of the hopper i1 before the pins 38 strike the sprockets 34.

One of the most important features :of the invention is the operative relationship between the blow ring and the filter bag. As shown in Fig. 1, itwill be noted that as the internal diameter of the ring'is less than the externaldiameter of the filter tube. when distended, the ring produces a concavo-convex portion in the felt as shown in detail in Fig. 4.

This has two important effects. First, it prevents the high pressure cleaning air escaping laterally without going through the .felt and performing its cleaningfunction. Another important effect is that the bending of the felt into concavo-convex form tends to open up the interstices on the inner wall of the filter; as well as crack ofi the layer 'of dust. deposited on the inner surface of the felt. This'bending and open-j ing of the pores. in the feltgreatly aids the cleaning of the filter. 7

If the ring is too small in diameter, it produces longitudinal creasing or fiuting of the filter tube all around its periphery. This interferes with proper contact between the ring and the filter tubeas well as increasing wear, unnecessarily.

If the ring is too large, much of the cleaning air f 4 will escape laterally and bending of the felt will be too slight to give really good results.

To enable the circumference of the blow ring to be adjusted to suit the dimensions of the particular filter tube with which it cooperates, the blow ring is made discontinuous. If a gap is left between the two adjacent ends of the ring, the felt will be pushed outwardly into such gap, causing fiuting or wrinkling with consequent heavy wear 7 along the tube opposite and adjacent to this gap. To avoid this difiiculty and, at the same time,

permit the circumference of the blow ring to be r r adjusted, the'ring is designed so that one end is in sliding telescopic engagement with the other.

Two forms of telescopic connnectionare illustrated in thedrawings. The first, that shown in Figsp5, 6 and 7, comprises a sleeve having an internal diameter equal to or slightly greater than the external diameter of the blow ring. As shown, this sleeve is formed from'a length of the same tube which is used for making the blow ring.

This length is slit longitudinally and then spread provided adjacent its ends'with transverseparti- 7 it to enter the ends of the blow ring.

circumferentially and a strip 45 soldered or welded over the gap so formed. The lower end of the sleeve, as shown in Figs; Sand 6, is soldered or welded onto one end of the blow ring. The upper end of the sleeve slides over the other end of the blow ring.

Adjustment is secured by a bolt 41 having eye 43 at one end located between a pair of lugs 38 soldered to the end of the sleeve 15 and pivotally secured to such'lugs' by a bolt 5%. .The other endof the bolt 47 which is threaded for the nuts 5| is passed through a lug 52 soldered to the blow ring.

In the modification shown in Fig. 8, the bridg ing sleeve 60 is designed. to fit inside of the ends of the blow ring. 'The sleeve may be formed from a length of' the same tube which is used in making the blow ring. Such length is slit longitudi nally and enough metalremovedso that, when the edges are brought together and soldered, its diameter has been reduced sufiiciently to permit The eye 6! of the adjusting bolt 52 is pivotally secured to lugs 63 soldered onto the lower end of the blow ring. passes through a lug 64 soldered end of the blow ring.

I claim: V 1

i. A self-cleaning dust filter of the type having a circular cleaning-air ring adapted to" be reciprocated up and dOWn the outside of a vertical filter tube, the inner diameter of the ring being less than the outer diameter of the tube when distended, in which the ring is discontinuous with one end in sliding telescopic engagement with the 7 other, and means for varying the degree'of overlap of such ends'to. change the inner circumfer ence ofthering. 1

2. A self-cleaning dust filter of the type having a circular cleaning-air ring adapted to here ciprocated up and down the outside of a vertical filter tube, the inner diameter of'the ring-being less than the outer diameter of the tube'when distended, in which the ring is discontinuous'and tions separated circumferentially to form a closed annular chamber nearly surrounding the filter tube and also provided with a part projecting beyond the partition in one "end toward and over lapping a portion of the other of said ends to bridge the gap between'such ends on th'efside fac ing the filter tube, and means for varying'the de The threaded end of theboltonto the upper gree of overlap to change the inner circumference of the ring.

3. A self-cleaning dust filter of the type having a circular cleaning-air ring adapted to be reciprocated up and down the outside of a vertical filter tube, the inner diameter of the ring being less than the outer diameter of the tube when distended, in which the ring is discontinuous and formed of two parts, a long one extending almost wholly around the filter tube and a short one extending only a short distance around the filter tube and having a radius of curvature equal to the radius of curvature of the surface of the long part with which it is in engagement, such short part being secured at one end to one end of the long part and having its other end in slidable telescopic relation to the other end of the long part to bridge the gap between the two ends of the long part, and means for varying the degree of overlap of such ends to change the inner circumference of the ring.

FREDERICK W. ARNOLD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

